It is commonly argued that delayed childbearing puts many women at risk of unintended childlessness, but determining how delay affects completed fertility is complicated by the fact that a large component of delay is attributable to choice: men and women make purposeful and deliberate decisions about when and how often to have children. However, it is also true that chance events--unanticipated or outside the control of the individual--may lead to undesired delay in childbearing, lower than desired completed family size, and even undesired childlessness. The research proposed here is a first step in assessing the respective roles of choice and chance in the determination of delayed childbearing and childlessness. Using the National Longitudinal Survey of Youth (NLSY79), this research will develop measures of underlying fecundity using data on prematurely terminated pregnancies; describe who delays childbearing by developing and estimating hazard models of time to first birth and subsequent birth intervals as a function of wages, income, education, fecundity, marital shocks, and demographic characteristics; and assess the extent to which delayed childbearing and childlessness is consistent with expectations.